Introduce WebTaskRunner Patch 1/5

Source/platform/blink_platform.gypi

 {
   'includes': [
     'platform_generated.gypi',
   ],
   'variables': {
     'platform_files': [
       'AsyncFileSystemCallbacks.h',
       'CalculationValue.h',
       'CheckedInt.h',
       'Clock.cpp',
@@ skipping 116 matching lines @@
       'Timer.h',
       'TraceEvent.h',
       'TraceEventCommon.h',
       'TracedValue.cpp',
       'TracedValue.h',
       'UUID.cpp',
       'UUID.h',
       'UserGestureIndicator.cpp',
       'UserGestureIndicator.h',
       'WebScheduler.cpp',
+      'WebTaskRunner.cpp',
       'WebThreadSupportingGC.cpp',
       'WebThreadSupportingGC.h',
       'WebThread.cpp',
       'Widget.cpp',
       'Widget.h',
       'WindowsKeyboardCodes.h',
       'animation/AnimationUtilities.h',
       'animation/CubicBezierControlPoints.cpp',
       'animation/CubicBezierControlPoints.h',
       'animation/TimingFunction.cpp',
@@ skipping 912 matching lines @@
       ['os_posix==1 and OS!="mac"',
         {
           'platform_test_files': [
             'text/LocaleICUTest.cpp',
           ],
         }
       ],
     ],
   },
 }